If a person cannot read a piece of literature without having a panic attack then perhaps they are not physically able to take a course in, say, English. It is up to the university to decide what it does with this kind of student: do they choose to not admit or graduate students who are incapable of completing the degree requirements? Do they tailor the degrees to students with special needs and make exceptions? Do they insist these students take a leave of absence and receive treatment before they continue?
All of these responses seem reasonable. If a student has such a unique life experience that they are not capable of completing standard university coursework, then the onus is on them to make that known to professors or administrators and come to some compromise. It is not the responsibility of the university to label and restructure its courses to acknowledge that there is a tiny fraction of the population that cannot participate in their education without severe distress.
Anything could be a trigger. Anything involving criminal justice could be a trigger for someone falsely (or rightfully!) imprisoned. A rape scene could be a trigger for a rape victim. Certain feminist literature could be a trigger for someone whose life was ruined through a false rape accusation. Someone who was recently dumped or cheated on could be triggered by discussing relationships. Perhaps a physics class triggers someone afflicted by severe existential angst -- entropy always increases? Domestic violence, child abuse, war, general violence, bullying, racism, torture -- many of these, things every college student should consider and think about before graduating -- are all triggers for someone.
So we should really put a trigger warning on every course. Better, let's make that trigger warning describe roughly what's going to be in the course and what students can expect out of it. Better yet, maybe put the grading scheme, reading list, and the rest of the administrative information about the course in it. We could call it some kind of nonsense word so as not to offend the people who hate trigger warnings or the people who love them. How about "syllabus".
Course syllabi already have a generally accurate description of course content so students may choose whether or not to expose themselves to any given material or prepare themselves.
The fact that a course is a college course and discusses human interaction at all should serve as enough as a trigger warning for anyone -- there could be triggering material in it. Period. Even if a class is about cold war economics, a student could bring up rape or racism in discussion.